docs: def get_annotationdefault(self):
          """
          The AnnotationDefault attribute, only present upon fields in an
          annotaion.
  
          reference: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.20
          """  # noqa
  
          buff = self.get_attribute("AnnotationDefault")
          if buff is None:
              return None
  
          with unpack(buff) as up:
              (ti, ) = up.unpack_struct(_H)
  
          return ti